There are plenty of places on Earth that seem alien to us, some we don’t even know much about. The deep sea is a perfect example: it’s been said that we know more about Mars than we do about the bottom of the ocean.

Hydrothermal vent communities weren’t discovered until 1977, well after the first landings on Mars. Scientists believed that the deep ocean was cold, dark, and inhospitable to life. But when scientists started studying the areas where hot mineral-heavy water wells up like an underwater geyer in tectonically active-regions (seafloor rifts), they were surprised to discover that deep-sea vents were home to thriving communities, full of life.

But they are dark, if not cold. If these deep sea communities had to subsist on detritus falling from the sunlit ocean surface, they would be more like cave organisms, rare, slow and sluggish in a low-energy environment. They weren’t: there were lots of animals, a high biomass, and many were active. Without photosynthesis, where does the energy come from?

The main animals featuring in the above photo are giant rift worms. They grow to be up to 1.5m long, the fastest-growing known marine invertebrate. They have a bright red top part and a whitish shell into which they can withdraw. They were originally put into their own phylum, the Pognophora (one of my favorite animal names ever), but sadly they were reclassified as part of the Siboglinidae, a larger group of worms. (I’m going to keep calling these giant rift worms Pogonophorans, if only because I know how to pronounce it.)

As if it weren’t strange enough to be living deep in the oceanic darkness, here’s the weird part: these critters have no mouth, no gut, and no anus. And what’s the advantage of being red in absolute darkness?

Giant rift worms are packed full of bacteria. Instead of relying on the energy from sunlight as photosynthetic organisms do, these chemosynthetic bacteria use hydrogen sulfide as an energy source for producing carbohydrates. The giant rift worms live off the products of these bacteria, in essence farming their own food inside themselves.

The red color is from hemoglobin, used to absorb hydrogen sulfide from the water and transport it to the bacteria. In mammals, hemoglobin is used to transport oxygen. Hydrogen sulfide is poisonous to us exactly because it bonds to the hemoglobin, blocking the oxygen. The pogonophorans have taken advantage of this transport capability, and have evolved a form of hemoglobin that successfully transports both hydrogen sulfide and oxygen.

Not all of the chemosynthetic bacteria are symbiotic. Free-living mats of bacteria form around the vents. All sorts of creatures live there, dining on bacteria: crabs, snails, fish, shrimp, and more. But most of them don’t dine as directly as the pogonophorans.

Although they don’t rely on the sun for energy, these communities do depend on sunlight in a more subtle way. Most of the organisms here get their oxygen from the surrounding water, and that oxygen comes from photosynthesis at the ocean surface. Still, these deep sea rifts offer science fiction writers a model of an ecosystem that could thrive on a moon of Saturn, or a planet with no life at the surface. The heat and chemical energy both come from geological processes. Pogonophorans also give us a model organism that doesn’t need to eat or excrete.

I also like the term Pogonophorans (beard-bearers). The use of this ecosystem in both astrobiology projections and SF is justified, since it has modifications across scales that are more exotic than most other systems on earth — including, I suspect, the “arsenic” bacteria recently hyped by NASA.

Thanks, Athena; I completely forgot to include the definition of Pogonophoran.

Deep sea rifts are fascinating, and there’s a whole ecosystem around these chemosynthetic bacteria. The arsenic-using bacteria, even if actually doing what NASA claims, are not part of a larger system.

Even the arsenate-metabolizing bacteria aren’t the base for much at all, because little else can live in high-arsenic anaerobic conditions. I’m most interested in the ecology of unusual systems as the basis for science fiction, rather than weird single organisms.

“Giant rift worms are packed full of bacteria. Instead of relying on the energy from sunlight as photosynthetic organisms do, these chemosynthetic bacteria use hydrogen sulfide as an energy source for producing carbohydrates.”

This struck me as really, really weird. I mean, an organism that is, essentially, little more than a host to other organisms but has a life and mind of its own. It’s like a city full of people, but the city itself is as alive as the people living in it.

But then, I remembered that we’re kind of the same. We’re just big hotels for bacteria and other organisms which, although keep us alive and well, aren’t there for our own benefit. Our continued life is a happy side-effect of their lives.

Well, okay. I know it’s not really weird because it’s one of the most basic relationships of biological organisms, as you say. But when I look at another organism–my girlfriend, say, or my cat–I see a whole, complete organism. A singular entity. I don’t see them as collections of symbiotic relationships any more than I see a glass of Coke as a collection of molecules. The article above makes the symbiotic relationship obvious and the idea–normal in the field of biology–struck me as weird because it’s not one I routinely have to think about. Especially in the case of the pognophora, because it seems the larger organism is so specifically designed to be an environment for the smaller organisms. (Of all the sciences, biology is easily my weakest so it’s where I’m going to make the biggest arse of myself )

We are actually complex colonies, and depend on our symbionts for survival. If you ever want to be very, very sick — get rid of your native internal flora and fauna. If you want to die, get rid of your mitochondria, which once were independent organisms. And if you want the planet to die, get rid of the symbiotes across all scales, starting with the chloroplasts that make photosynthesis possible (also once independent organisms).

This issue will be a major showstopper in long-term arcships, if we ever build and launch them. Kay and I discussed some aspects of this in my Crossed Genres interview.

You can certainly see your expertise within the work you write.
The sector hopes for even more passionate writers such as you who are not afraid to mention how they believe.
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